CHENNAI, INDIA
— Here in India's southernmost state of Tamil Nadu, a state ordinance banning "forced" religious conversions is setting up the conditions for a clash between the state's religious minorities and majority Hindu community.

On its face, the new law  which went into effect last Thursday and which punishes offenders with up to four years in prison  does not specify any particular religious group as its target. But members of Tamil Nadu's small minority communities  Christians, Muslims, and Buddhists  say the law is aimed at preventing lower-caste Hindus from converting to other religions.

"Christians do not believe in forced conversion  it is a sin; real conversion has to do with a change of the heart," says Bishop Devasagayam, head of the Anglican Church of South India in Chennai. "This ordinance is for political mobilization, and for political mobilization, you need to create an enemy," he says, referring to the minority community. "But we are confident that if we can put up a united stand against this law, no party can ignore the aspirations of 40 percent of the people."

Supporters of the law say that the best way to reduce tensions in India's multicultural society is to prevent aggressive missionaries from shifting the balances of power from one religious group to another. Some Hindu radical groups even say the law should be replicated nationwide. Detractors say that such measures only stir communal tensions and are a fundamental breach of the Indian Constitution's provisions for religious freedom.

Regardless, the debate's intensity reveals the extent to which religious and caste identity have become driving forces of this country. "In Indian society, there are two registers," says Dipankar Gupta, an anthropologist at Jawaharlal Nehru University in New Delhi. "On the political register, we don't recognize that the caste system exists, but on the social register, we do see caste differences."

The Prohibition of Forcible Conversion of Religion Ordinance is only the third of its kind in India. It includes a ban on the use of "allurements" to convert, but fails to define that term or what constitutes forced conversion in general.

"When we are feeding the poor, is that propagating our religion?" asks Bishop Devasagayam. "Anything a Christian does  whether it's teaching in schools or working in hospitals or slums  could be considered an 'allurement' to convert."

Promoted by former Tamil film star and current state Chief Minister Jayaram Jayalalitha, the new law could hardly have come at a worse time. In September, the US Committee for Religious Freedom issued a scathing report on India, citing in particular communal riots last spring in the state of Gujarat, which claimed the lives of 1,000 Indians, mostly Muslims.

Since that report, the country has witnessed a number of other brutal attacks on ethnic or religious communities, including the massacre of Hindu worshippers by two Muslim gunmen at a Hindu temple in Gujarat and the mob lynching this month of five outcaste Hindus in Haryana state for the "murder" and skinning of a cow.

Many Hindus say religious minorities themselves are causing trouble. In this state, for instance, the conversion of two villages  one to Christianity and the other to Islam  set off riots in 1981 that killed dozens. In recent months, the Seventh Day Adventist church has announced a campaign to convert 1,000,000 Hindus, particularly those from the Dalit community.

Dalits are those Hindus who are so far down on the social ladder that they cannot drink from the same cups as other Hindus or worship in the same temples. Indian law officially outlawed such vestiges of "untouchability," but in many rural parts of India, they are widely practiced.

"There is no ban at present for the social upliftment of the masses through education or hospitals, but in the name of social change, they should not convert people," says the Shankaracharya of Kanchi, a top Hindu teacher and saint, in an interview at his ashram in Kanchipuram, west of Chennai.

As one of the key proponents of Hindutva, or Hindu-ness, the Shankaracharya has preached that India's future lies in recapturing its past, a time when Hindu values and traditions held the countries many faiths, religions, and traditions together into a cohesive, Hindu-led whole.

But historians counter that such a period never truly existed, arguing that historically, Hindu leaders (as well as Muslim conquerors) more often used their political power to repress minorities.

While peddling Hindutva, the Shankaracharya has not been averse to talking with various communities, and he is widely credited with calming tensions in Gujarat last May. "I'm ready to have dialogue with Christians if they come, without any politicians," he says, crosslegged on a chair covered in leopard-print cloth. "Hinduism does not fight with anybody. But if a fight comes, Hinduism doesn't leave it."

For Tamil Nadu's religious minorities, that fight began long ago. After 2,000 years in India, they argue, Christianity can no longer be considered a "foreign" religion.

Most Christians in Tamil Nadu and neighboring Kerala believe that Christianity was brought to India by the Apostle Thomas around AD60 At Chennai's Santhome Cathedral, the supposed hand-bone of St. Thomas is kept.

At the same time, most Christians still believe that their role is to reform some of the more brutal aspects of caste oppression through social work and philanthropy.

That social development  found in 6,000 Christian schools statewide and countless hospitals, clinics, and social welfare centers  has had a profound effect on the livelihoods of South Indians, making them some of the most educated members of Indian society and guaranteeing good jobs in government bureaucracy and the growing world of high technology.

Social work has not necessarily filled churches. Official census figures show that the Indian Christian population has actually shrunk, from 2.4 percent in 1981 to 2.3 percent in 1991.

"Even if the conversion efforts are aggressive, it is good for the Dalit people," says Paul Pragasan, a Church of South India pastor in Chennai. "I look at this as social revolution. It's not so much a religious issue as it is social development from oppression to freedom, from illiteracy to literacy, and it is the upper class of the country who want to stop this."

For now, the ordinance has at least one achievement to its credit. It has united the fractious minority community, bringing together Christians, Muslims, Buddhists, and the millions of Dalits who make up nearly 40 percent of the state's population.

At a rally last week, on the grounds of the St. Andrew's Church in Chennai, thousands of Christians and Muslims gathered to hold a fast and protest the new law. It was the state's largest such protest or political meeting in recent memory.

"All these people here are those who live outside the system," says Mr. Pragasan, the pastor. "I'm a Dalit, he's a Dalit, he's a Dalit. This is not the intended purpose of the ordinance, but it has brought us together, and if we unite, we are the majority."